Single handle faucets, commonly referred to as mixer valves, that control the flow of both hot and cold water have seen vast consumer acceptance. The faucets are commonly constructed such that a handle or knob is movable in two distinct direction to adjust the mix of hot and cold water and to adjust the volume or flow rate.
The two basic types of mixer valves that have seen widest commercial acceptance are plate valves and ball valves. Ball valves are renowned for reliable and durable one piece valve construction that is easily assembled. Plate valves on the other hand offer a drive mechanism that allows motion of the handle in two distinct directions that has found widest commercial acceptance. This desirable handle motion allows for an orbiting motion of the handle about a fixed axis of the valve body and a rocking, i.e. pivoting motion about a axis that moves with respect to the valve housing as the handle orbits about the fixed axis. The moving axis is perpendicular to the fixed axis of the valve housing. A characteristic of this type of handle motion is that when the handle is pivoted to an off position, the mix ratio of hot and cold water can be remembered by the location of the handle so that when the faucet is turned back on, one has the option of obtaining the same mix of hot and cold water flows through the faucet.
Recently, ball valves have been devised that allow the handle to be operated in the same fashion as the above described plate type mixer valves. The system is disclosed in U.S. Pat. No. 4,449,551 issued to Lorch on May 22, 1984. Another system is disclosed in PCT application PCT/US91/07816 filed on Oct. 22, 1991 by the present applicant and is incorporated herein by reference.
Most plate type and ball type mixing valves have a control stem extending out from the valve housing and connectable to a handle to control the position of the valve. The extent of motion for controlling the maximum amount of flow and the maximum temperature of the water is commonly defined by the shape of the opening or by structures placed under an adjustment ring screwed into the cap member to tighten the valve assembly against leakage. The internal position of the volume and temperature limiters renders them difficult to change. Repair or replacement of the limit structures requires that the main water line be shut off from the valve. Often, the volume and temperature limiters are built into the guide mechanism of the valve itself which therefore requires the elements to be structurally resistant against any torquing forces not in the direction of motion of the handle. These forces are commonly referred to as lateral forces.
A limiting disc has been mounted in the valve housing for limited rotation about an axis of the housing. The disc has a slot through which a control stem extends. The control stem has a rectangular cross-section. The rectangular control stem engages two opposing edges of the slot to prevent relative rotation of the stem with the slot. In this manner, the limited rotation of the disc corresponds to the extent of rotation of the stem about the axis of the valve housing. The length of the slot limits the stems extent of rocking motion about a transverse axis. The need for a rectangular cross-sectioned stem increases the cost as compared with a standard circular cross-sectioned stem. Secondly, the rectangular shape provides larger dimensions of the stem a compared to a cylindrical stem and therefore hinders the reduction of the general dimensions of the faucet mixing valve housing. Thirdly, significant technological difficulties exist to have the rectangular control stem made integral with the ball valve. The rectangular control stem must be precisely oriented onto the ball valve element. A small angular discrepancy provides for a significant change in temperature control.
What is needed is a volume and temperature limiting device that can be applied to the exterior of the valve housing. Furthermore what is needed is a limiter device that is independent from the guide mechanism of the mixing valve faucet to provide for a system which can easily allow replacement of limiting elements for changing the volume and temperature field of the mixing valve without disassembly of the valve housing. It is further desired to have a limiter device that can be incorporated onto a cylindrical control stem of a faucet mixing valve.